Daoji Li

Suspended microplastics in the surface water of the Yangtze Estuary System, China: first observations on occurrence, distribution.

Levels of microplastics (MPs) in China are completely unknown. This study characterizes suspended MPs quantitatively and qualitatively for the Yangtze Estuary and East China Sea. MPs were extracted via a floatation method. MPs were counted and categorized according to shape and size under a stereomicroscope. The MP densities were 4137.3±2461.5 and 0.167±0.138 n/m(3), respectively, in the estuarine and the sea samples. Plastic abundances varied significantly in the estuary. Higher densities in three sea trawls confirmed that rivers were the important sources of MP to the marine environment. Plastic particles (>5mm) were observed with a maximum size of 12.46 mm, but MPs (0.5-5 mm) constituted more than 90% by number of items. The most frequent geometries were fibres, followed by granules and films. Plastic spherules occurred sparsely. Transparent and coloured plastics comprised the majority of the particles. This study provides clues in understanding the fate and potential sources of MPs.

The processes of dynamic sedimentation in the Changjiang Estuary

Abstract The characteristics of the mouth bar and subaqueous delta, and the water masses and water systems in the Changjiang Estuary and nearby coastal waters are examined. The hydrodynamics of the estuarine plume, and the fronts and turbidity systems are described with reference to their distribution and movement. Physical, chemical, biological and geological barrier effects of the estuarine mouth bar are evaluated. Through examination of the sediment distribution, sedimentation rate and depositional sequence, the sediment exchanges and evolution of the estuarine mouth bar and subaqueous delta are described.

Microscopic anthropogenic litter in terrestrial birds from Shanghai, China: Not only plastics but also natural fibers.

The level of contamination by microscopic anthropogenic litter (0.5-5mm) in terrestrial ecosystems is not well understood. After chemical digestion in 10% KOH, microscopic anthropogenic litter from the gastrointestinal tracts of 17 terrestrial birds was identified and categorized under a stereomicroscope based on its physical properties and melting tests. In total, 364 items from 16 birds were identified as microscopic anthropogenic litter, ranging in size from 0.5 to 8.5mm. No relationship between plastic load and body condition was found. Natural fibers, plastic fibers and fragmented plastics represented, respectively, 37.4% (136 items), 54.9% (200 items) and 7.7% (28 items) of total litter items. Small sample sizes limited our ability to draw strong conclusions about the metabolism of natural fibers, but the decline in the proportion of natural fibers from the esophagus to stomach to intestine suggested that they may be digestible. Particles smaller than 5mm represented more than 90% of the total number of pollutant items. Particles with colors in the mid-tones and fibrous shapes were overwhelmingly common particles. The results reflect pollution by microscopic anthropogenic litter in the terrestrial ecosystem of the study area. Microscopic natural fibers, which may disperse and adsorb chemical pollutants differently from microplastic and may pose an even greater risk, are in urgent need of further research.

Fluorescence characteristics of chromophoric dissolved organic matter in shallow water along the Zhejiang coasts, southeast China.

Twenty-eight surface water samples from rivers, muddy intertidal flats, sand shores, and bedrock coasts were collected along the Zhejiang coastline in southeast China. In addition, three samples from the Changjiang (Yangtze River) were collected for comparison. CDOM (chromophoric dissolved organic matter) absorption and fluorescence excitation-emission matrix (EEM) spectroscopy, as well as nutrients and DOC were measured in these samples. According to salinity, nutrient, and DOC constituents, the 28 Zhejiang samples were categorized into four groups, i.e. highly-polluted, river derived, muddy-flat derived, and saltwater dominated ones. Among the six parameters (two humic-like and two protein-like peak intensities in fluorescence EEM contours, absorption at 300 nm, and DOC concentration) for the Zhejiang samples, any two of them were positively correlated. The submarine groundwater discharge, rather than local rivers, might have provided most of the freshwater that interacted with the saltwater during the mixing process. The high protein-like EEM peaks in samples from muddy salt marshes and rivers were probably caused by terrestrial inputs, land-based pollution, and local biological activities in combination.

Medium resolution imaging spectrometer (MERIS) estimation of chlorophyll-a concentration in the turbid sediment-laden waters of the Changjiang (Yangtze) Estuary

Satellite estimation of chlorophyll-a (Chl-a) concentration in the Changjiang Estuary is challenging for ocean-colour retrieval algorithms. The Changjiang Estuary is characterized by suspended-sediment-dominated waters in the mouth and optically complex case 2 waters offshore of the mouth. Satellite ocean-colour products show that high-sediment loads of estuarine waters can cause overestimations or invalid flags of Chl-a concentration. A synthetic chlorophyll index (SCI) was designed for extracting chlorophyll information and for minimizing the influence of sediments on the remote-sensing reflectance spectrum. An SCI algorithm, a quadratic polynomial function of the SCI versus Chl-a concentration, was applied to the estimation of Chl-a concentration from Medium Resolution Imaging Spectrometer (MERIS) images. The overestimation of Chl-a concentration was corrected. The SCI algorithm has applications for MERIS estimation of Chl-a concentration in turbid waters with a moderate to high suspended-sediment concentration.

Stable isotope ratios of carbon and nitrogen in suspended organic matter: Seasonal and spatial dynamics along the Changjiang (Yangtze River) transport pathway

Seven cruises were conducted in the Changjiang (Yangtze River) Estuary and the adjacent western East China Sea (ECS) from 2010 to 2012 to study the seasonal variations of δ13C and δ15N in suspended organic matter. In addition, two cruises in the northeastern ECS in July 2011 and in Tsushima Strait in July 2012 were conducted to evaluate the distribution patterns of these isotopes over the entire Changjiang transport pathway. In summer, the surface δ13C was lowest in the Changjiang Channel, increasing from land to sea, reaching highest values in the central ECS, and then decreasing and remaining relatively constant. In winter, the surface δ13C in the western ECS showed lower values with less variation in general. At most stations, δ13C increased from the sea surface to the seabed, reflecting the degradation of sinking organic matter; however, these trends could be changed in the summer by surface phytoplankton accumulation. Combining data from all the Changjiang Estuary and western ECS cruises revealed that when the suspended particulate matter (SPM) was > 135 mg/L, the δ13C values were fairly constant (−24.5‰ to −20.5‰); when the SPM was < 135 mg/L, the δ13C values showed much greater variability (−28.4‰ to −16.6‰). The surface δ15N also showed generally higher values in the central ECS in summer and lower values in winter. The seasonal variations of δ13C and δ15N were largely attributed to the SPM composition change, i.e., more phytoplankton cells in the summer whereas more resuspended sediment particles were present in winter.

The chemokinome superfamily in channel catfish: I. CXC subfamily and their involvement in disease defense and hypoxia responses

ABSTRACT Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in regulating cell migration and activation. They are defined by the presence of four conserved cysteine residues and are divided into four subfamilies depending on the arrangement of the first two conserved cysteines residues: CXC, CC, C and CX3C. In this study, a complete set of 17 CXC chemokine ligand (CXCL) genes was systematically identified and characterized from channel catfish genome through data mining of existing genomic resources. Phylogenetic analysis allowed annotation of the 17 CXC chemokines. Extensive comparative genomic analyses supported their annotations and orthologies, revealing the existence of fish‐specific CXC chemokines and the expansion of CXC chemokines in the teleost genomes. The analysis of gene expression after bacterial infection indicated the CXC chemokines were expressed in a gene‐specific manner. CXCL11.3 and CXCL20.3 were expressed significantly higher in resistant fish than in susceptible fish after ESC infection, while CXCL20.2 were expressed significantly higher in resistant fish than in susceptible fish after columnaris infection. The expression of those CXC chemokines, therefore can be a useful indicator of disease resistance. A similar pattern of expression was observed between resistant and susceptible fish with biotic and abiotic stresses, ESC, columnaris and hypoxia, suggesting that high levels of expression of the majority of CXC chemokines, with exception of CXC11 and CXC20, are detrimental to the host. HIGHLIGHTS17 CXC chemokine genes were identified in channel catfish genome.The fish‐specific and the expansion of CXC chemokines in the teleost genomes were revealed.The expression of CXC chemokines showed a gene‐specific manner after bacterial infections.The expression of CXC chemokine genes showed a gene‐specific pattern under hypoxia.

Long-term changes in the Changjiang Estuary plankton community related to anthropogenic eutrophication

The Changjiang River is well-known to channel significant anthropogenic influences to the estuary. However, long-term changes in plankton community related to anthropogenic eutrophication in the estuarine water are not well documented. In this paper, data from a nine year study (1996, 1998–2005) on suspended matter, chemical oxygen demand, nutrients and plankton community were collected and analyzed by principal component analysis. These data reveal that N/P ratio was always much higher than 40 and Si/N ratio decreased from 1.35 to 0.94 between 1996 and 2005. As an ecological consequence to such nutrient balance changes, phytoplankton species diversity and the dominance of diatoms decreased, dinoflagellates increasingly dominated the phytoplankton population, and the frequency of harmful algal blooms caused by dinoflagellates also increased. Furthermore, due to the reduced diatom availability, the dominance of copepods decreased, zooplankton diversity increased, and medusae increasingly dominated the zooplankton population. Water column nutrient ratios, therefore, are also important factors affecting anthropogenic eutrophication, as are the contamination loadings from land.

Effects of irradiance and phosphate on growth of nanophytoplankton and picophytoplankton

Abstract In situ incubation experiments were conducted to investigate the phosphate uptake and the growth variations of nano- and picophytoplankton under controlled phosphorus concentrations and irradiances in Changjiang estuary and its adjacent sea in China. The results showed that the rates of phosphate uptake were accelerated at high levels (0.60 μmol/L) under the condition of 100% natural irradiance, and the cell densities of nanophytoplankton and Synechococcus spp. obviously increased, whereas picoeukaryote was adapted to low phosphate levels (0.25 μmol/L). Under low irradiance (50% of natural irradiance), uptake of phosphate was restrained at high levels, and the growth of both nanophytoplankton and Synechococcus spp. was also limited. Morerover, nanophytoplankton and Synechococcus spp. grew well at intermediate phosphate levels (0.41 μmol/L), whereas picoeukaryote grew well at low phosphate levels. In addition, the growth period of phytoplankton at intermediate phosphate levels was obviously prolonged, suggesting that the limitation of phytoplankton growth mainly reflected the changes during its growth period. In the absence of irradiance, the addition of phosphate did not affect the release rates of phosphate with a linear increase in the phytoplankton, whereas the growth rates of the phytoplankton showed an exponential decrease, which showed that phosphate regeneration was faster during day than during night; therefore, the irradiance was a significant factor that affected phosphorous biogeochemical cycle in the Changjiang estuary in China.

The chemokinome superfamily: II. The 64 CC chemokines in channel catfish and their involvement in disease and hypoxia responses

&NA; Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in regulating cell migration and activation. Based on the arrangement of the first four cysteine residues, they are classified into CC, CXC, C and CX3C subfamilies. In this study, a complete set of 64 CC chemokine ligand (CCL) genes was systematically identified, annotated, and characterized from the channel catfish genome. Extensive phylogenetic and comparative genomic analyses supported their annotations, allowing establishment of their orthologies, revealing fish‐specific CC chemokines and the expansion of CC chemokines in the teleost genomes through lineage‐specific tandem duplications. With 64 genes, the channel catfish genome harbors the largest numbers of CC chemokines among all the genomes characterized to date, however, they fall into 11 distinct CC chemokine groups. Analysis of gene expression after bacterial infections indicated that the CC chemokines were regulated in a gene‐specific and time‐dependent manner. While only one member of CCL19 (CCL19a.1) was significantly up‐regulated after Edwardsiella ictaluri infection, all CCL19 members (CCL19a.1, CCL19a.2 and CCL19b) were significantly induced after Flavobacterium columnare infection. In addition, CCL19a.1, CCL19a.2 and CCL19b were also drastically up‐regulated in ESC‐susceptible fish, but not in resistant fish, suggesting potential significant roles of CCL19 in catfish immune responses. High expression levels of certain CC appeared to be correlated with susceptibility to diseases and intolerance to hypoxia. HighlightsA total of 64 CC chemokine genes were systematically identified and characterized in channel catfish genome.The fish‐specific CC chemokines and the expansion of CC chemokines in the teleost genomes were revealed and identified.CCL19 might play significant roles in catfish immune activities.High expression levels of certain CC appeared to be correlated with susceptibility to diseases and intolerance to hypoxia.